Proceedings of 1st International Symposium for Color Science and Art 2019

Scientific Research into the Green Metallic Luster ofSafflower Red Pigment extracted by Traditional MethodHitoshi YAJIMA, Maiko SASAKI, Keiko TAKAHASHI, Masato OSHIMA,
Kazuyuki HIRAOKA, Morio YASHIRO, Katsumi YAMADA,Tokyo Polytechnic Univ., 1583 Iiyama, Atsugi, Kanagawa 243-0297, JapanABSTRACT

3. RESULTS AND DISCUSSION
Figure 1 shows the photograph of the safflower red
pigment film (thickness : 0.4 μm) on the quartz crystal
plate as the result in photo-illumination though multi-color
filter for 30 min. After the photo-illumination, the greenish
metallic luster turned red color. The biggest changing was
found at none filter part, and the secondary big changing
was found under the green filter part. On the other hand,
the metallic luster was left as before under the red filter
part. The specular reflectance spectra of the pigment film
was measured after the photo- illumination via color filters.
The reflectance values at the wavelength of 550 nm werelowered in the order of none filter, green filter, orange filter,
red filter and unexposed part. The absorption spectra ofthese filters and the red pigment film were measured.
These results indicated that the red filter can cut the lightat the all absorption band of the red pigment, and theorange filter can though the light at the longer wavelength
regions of the red pigment. Therefore, it was confirmedthat the absence of the metallic luster was induced by thephoto-illumination with the visible light at the absorption
band of the red pigment. On contrary, the change in theabsorption spectrum of the red pigment film could not befound in the least by the short time exposure for 30 min.
According to the result, the deterioration of the pigment
associated with the absence of the metallic luster probably
took place only the uppermost surface layer of the film by
the photo-illumination.
Then, the film thickness of the pigment was reduced toabout 80 nm, the photo-illumination time was extended to
139 min. Figure 2 shows the photograph of the pigment
film after the long photo-illumination. In the case of theblack color substrate (for reflection evaluation), thegreenish metallic luster was observed in the unexposedpart, and the color change from red to reddish orange wasinduced by the photo-illumination. By the observation withthe white substrate (for transmission evaluation), the colorof the pigment film turned the orange color by thephoto-illumination. As the result, considerable color
changes were achieved by the film thinning and theextended photo-illumination time. Figure 3 shows thespecular reflectance spectra of the pigment film (80 nm)
before and after the photo-illumination (139 min.). In
comparison with the rate of decrease in the reflectance atthe 550 nm (-40%) for the thick film (0.4 μm) illuminated for
30 min. (Fig.2), the reflectance value at the wavelength of

A visible photo-illumination to the carthamin red pigment
solid film was carried out in the study. It was found that thegreenish metallic luster of the film was weaken by thephoto-illumination, and the absorption of the film was also
weaken at the same time. Because the deterioration of
the carthamin chromophores was induced by thephoto-illumination, the absorption in the green light band
was probably an important factor of the metallic luster
generation.
1. INTRODUCTION
Pigments obtained from safflower (Carthamustinctorius L.), has been used as herbal medicine, food,colorant and cosmetics. There are some difficulties (suchas thermal decomposition and photo-fading) in theextraction of carthamin (red pigment) from the petal, it isdifficult to separate the water-soluble yellow pigment andthe water-insoluble red pigment. Therefore, the red
pigment is quite rare, and it is hard to obtain the purecommercial products. Kuroda reported in her paper thatthe red pigment solid with a high purity gave a greenish
metallic luster.[1] Although the optical properties and thephoto-fading characteristics of the red pigment wereevaluated with a mixture sample such as the dyed textiles
or liquid phases at the lower concentrations, there isalmost no discussion on its solid phase at the higherpurities. [2,3] In this study, photo-illumination for the solid
film of the safflower red pigment was carried out to discuss
the relationship between the absorption of thechromophores and the reflection.
2. EXPERIMANTALThe safflower red pigment was extracted by atraditional method with some modifications. [4]The pigment
film was immobilized onto the quartz crystal plate bycasting from the concentrated aqueous solution of theextracted pigment. These films were dried under dark andambient atmosphere at room temperature.
Thephoto-illumination for the pigment film was carried out witha metal-halide lamp (incident power: 30 mW) underhumidified condition.
Specular reflectance andtransmittance spectra were obtained by a CCD array
spectrometer connected with fiber optics. Changes in thechemical structures of the red pigment by thephoto-illumination were evaluated with a Fourier transform
infraredspectrometer(FT-IR)and a Raman
micro-spectrometer.

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Proceedings of 1st International Symposium for Color Science and Art 2019550 nm remarkably decreased (-70%) by thephoto-illumination. The spectrum shape  after the(a)remarkably decreased after the photo-illumination. The
carbonyl group is part of the chromophore of the carthamin(red pigment).[5-8] Figure 4 shows the Raman spectra of
the pigment film before and after the photo-illumination.
The clear changes were found between the two spectra,
especially, the absence of the strong signals 1176 cm -1(substituted aromatic) and 1600/1620 cm-1 (C=C ring
stretch doublet) was found between before and after theWith these results, it wasphoto-illumination.[9,10]
confirmed that the deterioration of the carbonyl group and/or the shortening of the π-conjugation were induced in thechemical structures of the red pigment by thephoto-illumination. These discussions probably contributeto make sure that the greenish metallic luster of the red
pigment film was directly associated with the lightabsorption of the chromophores.

(b)Fig. 1 Photograph of the safflower red pigment film
(thickness : 0.4 μm) on the quartz crystal plate
demonstrating the effect of photo-illumination
through multi-color filter for 30 minutes. (a) Fig. 2
Photograph of the pigment film (thickness : 80 nm)
after the long (139 min.) photo-illumination.(b)Fig. 3 Specular reflectance spectra of the pigment film
(thickness : 80 nm) before and after thephoto-illumination.

Fig. 4 Raman spectra of the pigment film (thickness :80 nm) before and after the photo-illumination.
6. REFERENCES[1] C. Kuroda, Proceedings of the Imperial Academy, 5,32 (1929).
[2] H.Oda, Color. Technol., 117, 204 (2001).
[3] R. Laursen, C. Mouri, e-PS, 10, 35 (2013).
[4] H. Yajima, M. Sasaki, K. Takahashi, K. Hiraoka, M.
Oshima, K. Yamada, J. Soc. Photogr. Sci. Technol.
Jpn., 81, 2 (2018).
[5] T. Kanehira, A. Naruse, A. Fukushima, K. Saito, Z
Lebensm Unters Forsch, 190, 299 (1990).
[6] K. Kazuma, T. Takahashi, K. Sato, H. Takeuchi, T.
Matsumoto, T. Okuno, Biosci. Biotechnol. Biochem.,
64, 1588 (2000).
[7] Y. Shin, D. II Yoo, Textile Coloration and Finishing,24, 165 (2012).
[8] S.-J. Yue, C. Qu, P.-X. Zhang, Y.-P. Tang, Y. Jin,J.-S. Jiang, Y.-N. Yang, P.-C. Zhang, J.-A. Duan, J.
Nat. Prod., 79, 2644 (2016).
[9] C. M. Schmidt, K. A. Trentelman, e-PS, 6, 10 (2009).
[10] A. Cesaratto, Y.-B. Luo, H. D. Smith II, M. Leona,Herit. Sci., 6, 22 (2018).
[11] B. G. Anex, W. T. Simpson, Review of Modern
Physics, 32, 466 (1960).
photo-illumination had a curved part convex downward
covering the green light band. The transmittance spectraof the pigment film were evaluated before and after thephoto-illumination. The absorption of the red pigment
around the wavelength of 550 nm was remarkably
weakened by the photo-illumination, and the absorption
maximum shifted to 480 nm was found on the resulting
spectrum. The orange state (λmax：480 nm) is different
from a yellow pigment having the absorption maximum
around 410 nm. As a general understanding, the redcolor of carthamin was obtained by expansion of theπ-conjugation due to coupling with the yellow molecules.
It was suggested that this orange state is not due to asimple recovery of yellow pigment, but to a different type ofdecomposition products of the red pigment. In order tostudy the change in the chemical structures of the red
pigment, the measurement of the rotation and vibration
spectra were carried out with a FT-IR and Raman
spectrometer. As the obtained spectrum from the FT-IR
measurement, some signals at 1515, 1585, 1624 cm -1 dueto conjugated aromatic C=O (carbonyl group) stretching52